The invention relates to an installation for coating objects with powder, in particular for powder painting, having
a) a booth, in which powder can be applied to the objects by at least one application device;
b) an air supply device, with which air can be introduced into the booth,
c) an extraction device, with which a mixture of air and excess powder can be extracted from the interior of the booth via at least one mixture outlet situated in the bottom; and
d) a plurality of filter units, which can be selectively moved under the mixture outlet of the booth and which each have a filter separating the powder from the air.
In the coating of objects with powder, in particular in powder painting, it cannot be avoided that a considerable part of the powder leaving the application device does not adhere to the objects to be coated. It is known to recover this excess powder (frequently called xe2x80x9coversprayxe2x80x9d) to a large extent by means of an air stream flowing through the booth from the top downwards. In the process, the air stream takes up the stray excess powder. A mixture of air and powder is extracted via a mixture outlet situated in the bottom and is led to a filter unit in which the powder is separated from the air/powder mixture in order to be passed on for reuse.
If a frequent change of the powder being used, for example a change of the colour of the painting powder, is required, it is not economical to clean the filter units each time. Rather, it is known in this case to provide a plurality of movable filter units which are each intended for a particular type of powder, thus for example one powder colour. In each case that filter unit is coupled to the mixture outlet of the booth which is intended for using that type of powder which is currently being employed in the booth. On changing the type of powder, only the filter unit active at the time needs to be replaced by another filter unit.
In known installations of the type mentioned at the outset, the filter units had wheels for rolling on the room floor. However, this was not without problems in terms of handling: on the one hand, the filter units exhibited a not inconsiderable rolling resistance, in particular on changing direction, on the other hand, with an uneven room floor, exchanging the filter units involved adjusting work. On changing the colour, not only did the filter unit have to be laboriously exchanged, but the entire booth and its outlet funnels also had to be cleaned.
The object of the present invention is therefore to design an installation of the type mentioned at the outset in such a way that exchanging the filter units on changing the type of powder is simplified.
This object is achieved according to the invention in that
e) the filter units can be moved while suspended from a supporting-rail system.
Since, according to the invention, the filter units are suspended from the supporting-rail system, they do not need to follow the course of the floor any longer. This has two consequences: the height at which the filter units move is predetermined by the supporting-rail system. Readjustment on connecting a new filter unit is thus no longer necessary. The evenness of the rolling surfaces predetermined by the supporting-rail system means that only small forces are required on moving the filter units.
It is expedient for the supporting-rail system to have a plurality of parking positions at each of which a filter unit can be kept in readiness. The basic construction of such a supporting-rail system can thus resemble a xe2x80x9cmarshalling yardxe2x80x9d. It can optionally be designed such that any filter unit can reach any parking position. Alternatively, however, it is also possible to design the supporting-rail system so that each filter unit is assigned a specific parking position. The parking positions can differ from the other regions of the supporting-rail system in that they have devices for stopping the filter units and/or for detecting the presence of the filter unit.
In their xe2x80x9cactivexe2x80x9d working position beneath the mixture outlet of the booth, the filter units must of course be open at the top. However, during the times when they are placed in readiness in a parking position, each filter unit should be closable by a cover in order to avoid fouling.
For this purpose, there may be provided, at each parking position for example, a cover which can be placed against the inlet of the filter unit situated in the corresponding parking position. This cover is therefore assigned permanently to a particular parking position and not to a particular filter unit.
It is of course also possible for each filter unit to be provided with a removable cover, in which case the cover moves along with the filter unit. By way of example, the cover can be pivotably attached to the filter unit.
Particular preference is given to that embodiment of the invention in which the inlet of each filter unit is formed by a bellows which is expandable in the vertical direction and carries a seal. The filter unit which is xe2x80x9cactivexe2x80x9d at the time is therefore connected to the mixture outlet of the booth by extending the bellows upwards and placing the seal against the mixture outlet of the booth.
In this case, there can be attached to the upper border of the bellows a sealing frame, on which the seal is fastened and which is movable in the vertical direction by means of a drive device. A piston/cylinder unit in particular is suitable as the drive device.
Finally, it is expedient for there to be provided on the rail system at least one cleaning position, at which devices serving to clean the filter units are arranged. Extraction and blow-out fans in particular, optionally also appliances operating with liquid cleaning agents, are suitable as such devices. If a particular type of powder is no longer required in the installation for some time and it is therefore no longer necessary to reserve a particular filter unit for this type of powder, the filter unit in question can be brought into the cleaning position on the rail system, where it can be cleaned thoroughly to remove the old type of powder and in this way prepared for use with another type of powder.